An experimental study of the effect of the flow in fractures on rainfall-runoff mechanism

Abstract

A large-scale sprinkling experiment, using a 625 cm of slope having tubes at middle slope, simulating bedrock fissures, has been conducted to evaluating the role of bedrock fissures on subsurface water movement and runoff generation mechanisms. By drilling through the bottom of the container we made a 6-mm hole on the slope and connected 10 tubes simulating fractures. Each tube had a hemp cord in it, so it has considered the “quasi-fractures” that that resembles hydraulic property of a real fracture surface. Both runoff from the sands and flow in the tubes were measured manually using a measuring cylinder. The data on soil moisture, water-table elevation, and piezometric head were also collected. The runoff peaks were found to be much greater than the tube flow peaks. However the tube flow peaks always coincides with the recession stage of runoff when the runoff was very small ; the volume of tube flow was as much as half of the runoff. This suggests the possibility that the fracture flow in bedrock has a large effect on rainfallrunoff mechanism.